1. Field of the Invention
The present invention relates to the clinical medicine field, especially to a bone morphogenetic protein-2 active peptide. The present invention also relates to a method for manufacturing the active peptide and the application on medicine for promoting osteogenesis and repairing bone defect.
2. Description of the Related Art
According to statistics, there are 3 million patients suffering from bone defect or bone injury due to various factors, such as traffic, production safety accident and bone disease, associated with the increasing trend year by year. Thus, the demand of substantial bone repair materials is urgent, and the market is huge. With the advancement of technology, via the implementation of clinical autologous or allogeneic tissue transplantation and the use of synthetic bone tissue substitutes, great progress has been made on the treatment of these diseases. However, there also exist the disadvantages that are the expense of individual normal tissues, the shortage of donor source, expensive price, and the problems of rejection and secondary infection, which could not meet clinical requirements. At present, how to fundamentally solve the repair of bone defects has become the international medical leading issue.
In recent years, the use of tissue engineering techniques, namely via composite transplantation or separate implantation of extracellular matrix materials, cell growth factors and seed cells to repair bone defects, has drawn many countries' great attention. However, corresponding researches about bones at home and abroad are still at the beginning stage, accordingly many problems remain to be solved, in which one of key problems is how to develop remarkable medicines or materials of repairing bone defects.
Bone morphogenetic proteins, namely BMPs for abbreviation, are glycoprotein polypeptides in bone matrix, which include the disulfide bond structure. Bone morphogenetic proteins, the relative molecular mass being 18000-30000, constitute a peptide factor family exhibiting similar structure and functions expect BMP-1. So far, 43 kinds of bone morphogenetic proteins in the family have been found. Bone morphogenetic protein is the only local growth factor that can solely induce the formation of bone tissue, inducing undifferentiated mesenchymal cells in vivo into cartilage and bone. Bone morphogenetic proteins exhibit different abilities of induced osteogenesis, in which bone morphogenetic protein-2 has been studied extensively and has greatest osteogenesis ability.
However, BMP-2 is a powder-efficient material, which could not be evenly distributed in the bone defects and exhibits no function of supporting. Moreover, BMP-2 has a short half life in vivo and metabolizes quickly when local application. Thus, relative high dose is essential to stimulate sufficient osteogenesis for persistent therapy effect. Accordingly, clinical therapy cost would increase, and it is possible to cause toxicity. Large-scale production of BMP-2 and more wide clinical application have always been difficult for current research.
At present, techniques such as molecular biology and genetic engineering are used at home and abroad for production of recombinant human bone morphogenetic protein-2 (rhBMP-2). However, due to complexity of equipments and preparation techniques, long production cycle, low yield and expensive price, it is difficult to achieve large-scale production, and also exists safety problems of genetic engineering products (Wozney J, Seeherman H. Protein-based tissue engineering in bone and cartilage repair. Curr Opin Biotechnol, 2004, 15(5): 392-398.). For clinical application, inorganic materials, polymers, biological materials, composite materials and the like are used as BMP-2 or rhBMP-2 vectors for treatment. Nevertheless, for various materials, there are differences in many aspects, such as biocompatibility, mechanical property, osteoconductivity, osteoinductivity, plasticity and degradability. But there are still no substitutes for bone tissues, which can meet the requirements of perfect materials of repairing bone defects. In this way, the applications of extrinsic BMP2 or rhBMP-2 on fracture therapy are limited. In addition, macromolecular proteins would randomly enfold when adhered to material surfaces, so that the bioactivity is not high because of insufficient exposure of active sites.
Another method is to transfer BMP-2 gene into mesenchy mal stem cells using transgene technology and express BMP-2 by transgenic cell. As the recent reports described, vectors of bone morphogenetic protein-2 gene are mostly adenovirus, in which virus vectors could cause harm to hosts through persistent proliferation. For host genes, the mutation risk also exists due to the intervention of extrinsic genes; extrinsic genes, transferred by non-virus vectors, would not be integrated into chromosomes of host cells, not causing excessive expression and deactivation of genes on entry sites. Thus, there is no insertion mutation risk, but less efficient expression. In addition, the time and quantity of gene expression in vivo could not be artificially controlled. But there are still disadvantages such as low transfection efficiency, short expression and potential carcinogenicity of virus vectors. (Chadderdon R, Shimer A, Gilbertson L. Advances in gene therapy for intervertebral disc degeneration. Spine J. 2004, 4 (6 Suppl): 341S-34.). Therefore, gene therapy on the basis of BMP-2 is still far from clinical application.